When to Fertilize Bougainvillea

Timing is everything when fertilising bougainvillea. Apply fertiliser too often or at the wrong stage and you’ll end up with leafy growth but few flowers. Fertilise too little and the plant weakens, producing fewer bracts. The best results come from fertilising consistently during active growth and adjusting the formula as the plant moves between leafy expansion and flowering cycles.

Seasonal Feeding Guide

Bougainvillea thrives when fertilised in rhythm with the seasons. In Australia and similar climates, growth and flowering usually follow warm-season cycles, with brief rest periods during winter.

Spring: Begin feeding regularly as new growth emerges. Balanced fertiliser strengthens roots and stems for the season ahead.
Summer: Continue feeding consistently, as this is the main flowering season. Use fertiliser every 2–3 weeks in pots and every 3–4 weeks in the ground.
Autumn: Bougainvillea often has a second flush of blooms. Maintain fertiliser to extend colour into the cooler months.
Winter: Growth slows, but light feeding keeps the plant healthy. Reduce frequency rather than stopping completely, especially in warm regions where the plant stays semi-active.

This cycle ensures bougainvillea has the energy to produce repeated flushes of bracts while maintaining strong roots and foliage year-round.

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How Often and What Fertiliser to Use

Frequency matters just as much as timing. Bougainvillea prefers steady, light feeding rather than heavy doses. Consistency keeps it balanced between growth and flowering.

Feeding frequency:

In the ground: every 3–4 weeks during active growth and flowering.
In pots: every 2–3 weeks since nutrients leach out quickly.
Rest periods: in winter, reduce to once every 6–8 weeks if growth slows.

Fertiliser options:

NPK 20-20-20: Best for balanced feeding throughout the year, supporting roots, leaves, and flower initiation.
NPK 4-18-38 + Calcium & Magnesium: Best during peak flowering cycles, boosting colour intensity and extending blooms.

Both fertilisers can be alternated: use NPK 20-20-20 to maintain strength, then switch to 4-18-38 + CaMg when blooms are forming.

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Fertilising Tips, Mistakes to Avoid, and FAQs

Over-fertilising with nitrogen is the most common mistake, leading to dense leaves with little colour. Another error is feeding inconsistently, which causes weak growth spurts instead of steady development. Always dilute fertiliser at 4ml per litre of water and apply after watering to protect roots.

CompleteGrow’s All Purpose Plant Liquid Fertiliser (NPK 20-20-20) is ideal for year-round feeding, while the Advanced Formula NPK 4-18-38 + Calcium & Magnesium ensures heavy flowering. Together, they provide a complete feeding solution across all growth stages.

Frequently Asked Questions

When is the best time of year to fertilise bougainvillea?
Spring through autumn during active growth and flowering. Winter feeding can be reduced but not always stopped.

How often should I fertilise bougainvillea?
Every 3–4 weeks in the garden, every 2–3 weeks in pots. Reduce in winter if growth slows.

What fertiliser works best for bougainvillea?
NPK 20-20-20 for steady health, and 4-18-38 + CaMg during bloom cycles for stronger flowers.

Can I fertilise bougainvillea in winter?
Yes, but at reduced frequency. In warmer regions, where the plant stays semi-active, continue light feeding to maintain strength.